K8S 问题排查：cgroup 内存泄露问题

unable to ensure pod container exists: failed to create container for [kubepods besteffort pod5f26dae8-0421-4eab-a3f7-aa51c6848e2b] : mkdir /sys/fs/cgroup/memory/kubepods/besteffort/pod5f26dae8-0421-4eab-a3f7-aa51c6848e2b: cannot allocate memory

查看 linux 内核

1cat /proc/version
2uname -a

可以发现 linux 版本是 3.0 版本

原因

cgroup 的 kmem account 特性在 Linux 3.x 内核上有内存泄露问题，然后k8s用了这个特性，导致后面创建不出新的pod来了

解决方法

1# 修改/etc/default/grub 为
2GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rhgb quiet cgroup.memory=nokmem"
3#加上了 cgroup.memory=nokmem
4# 生成配置
5/usr/sbin/grub2-mkconfig -o /boot/grub2/grub.cfg
6
7# 重启机器
8reboot

验证

1cat /sys/fs/cgroup/memory/kubepods/burstable/pod*/*/memory.kmem.slabinfo

输出信息

 1cat: /sys/fs/cgroup/memory/kubepods/burstable/pod0fe273ca-42e0-4223-9fe8-16d8dd1774e9/0fdd5d9c16929fd600dbdf313b5c3ebabad912dc0cb076ed6e7799e028b31481/memory.kmem.slabinfo: 输入/输出错误
 2cat: /sys/fs/cgroup/memory/kubepods/burstable/pod0fe273ca-42e0-4223-9fe8-16d8dd1774e9/aa30198d0c5413b70bf488c9daa350a85c7fc6b677235c5adaf2dde6caf95ec4/memory.kmem.slabinfo: 输入/输出错误
 3cat: /sys/fs/cgroup/memory/kubepods/burstable/pod5be86c5d-d012-4cc2-b693-4882a15eda90/059b26b00f4f286b0f52e759b83dad79c7676e1705ee0f3f175a277fd1e5ea5a/memory.kmem.slabinfo: 输入/输出错误
 4cat: /sys/fs/cgroup/memory/kubepods/burstable/pod5be86c5d-d012-4cc2-b693-4882a15eda90/bfa9db0c23fd056a0c05ee5b2b377dd551451cc0f18ddd5db82f9693674a4677/memory.kmem.slabinfo: 输入/输出错误
 5cat: /sys/fs/cgroup/memory/kubepods/burstable/pod8f588e3d-fe89-4716-ab36-3ef606c70367/6fab9f4f7a83bf4c79a68277b214807bd566a8f13212a0fdb5742e4eee4d75d5/memory.kmem.slabinfo: 输入/输出错误
 6cat: /sys/fs/cgroup/memory/kubepods/burstable/pod8f588e3d-fe89-4716-ab36-3ef606c70367/b04594732f7e38a47500ffe1150705110cfa683b585aa7eaf0965cc48ba2a46d/memory.kmem.slabinfo: 输入/输出错误
 7cat: /sys/fs/cgroup/memory/kubepods/burstable/pod9c449bdf-492b-4adc-a623-4ced323ac6d4/c9e73e56ddae0c6c301e43852a51165419eb293b05fa65407f8cb3fe449daf5d/memory.kmem.slabinfo: 输入/输出错误
 8cat: /sys/fs/cgroup/memory/kubepods/burstable/pod9c449bdf-492b-4adc-a623-4ced323ac6d4/d7392b1e4be1728fd739dc7117e6efc723a4727f143b91a1b386ad35dc1d3a2e/memory.kmem.slabinfo: 输入/输出错误
 9cat: /sys/fs/cgroup/memory/kubepods/burstable/podd316acd7-69fe-4ad5-963a-6e19174b7cb0/0ec18ac0509e6ab454ebe637bde002330afc9eb70eff6f23fe8caa12880e82f6/memory.kmem.slabinfo: 输入/输出错误
10cat: /sys/fs/cgroup/memory/kubepods/burstable/podd316acd7-69fe-4ad5-963a-6e19174b7cb0/dc5be82c01802c349c9505375c37dc054898b9b84e57cb4e671044e8a6459aac/memory.kmem.slabinfo: 输入/输出错误